As an example of a semiconductor device in which a main current flows in a direction of the thickness of a semiconductor substrate, a structure is suggested where an IGBT (insulated gate bipolar transistor) element and a diode element in parallel connection with the IGBT element are adjacently formed.
For example, Japanese Patent Application Laid-Open No. 11-097715 discloses an example where gate electrode structures are formed on a first main surface side of a semiconductor substrate, P type impurity regions and N type impurity regions are alternately and adjacently formed in a surface of a second main surface, the P type impurity regions and the gate electrode structures constitute an IGBT region, and the N type impurity regions and the gate electrode structures constitute a diode region.
In such a structure, since the P type impurity regions and the N type impurity regions on the second main surface side are in contact with each other, for example, a phenomenon called snapback occurs, resulting in a loss of energy in a switching operation of an IGBT element, thereby leading to an inability to obtain desirable electric characteristics.